This invention relates to an apparatus for inspecting the irregularity of a side wall surface of a tire to discriminate the quality of the tire.
It has been known that due to uneven intervals of ply cords, uneven overlapped amounts of ply joint and other causes, irregularities arise on a side wall surface of a tire when the tire is filled up with air. Such irregularities give bad influence to the uniformity of a tire and also mar the outside appearance to lower the marketability of the tire. For these reasons, it has been required to detect undesirable irregularities on the side will surface of the tire in inspection stage.
However, in addition to irregularities which are required to detect, there are irregularities caused by letterings, codes, marks, spews, dirts on a tire side wall surface, and the like which are not required to detect. Accordingly, it could be seen that it is necessary to separate signals generated by such irregularities as not required to detect from those generated by irregularities required to detect.
A conventional apparatus for inspecting the irregularity of a side wall surface is disclosed in Japanese Examined Patent Publication No. 62-30361. The conventional apparatus which utilizes an electrostatic capacity sensor can obtain no more than an averaged value in an area having a great circumferential length for example, exceeding 1 mm due to performance characteristics of the electrostatic capacity sensor and consequently provides inaccurate inspection. In the conventional apparatus, to eliminate signals caused by detection-unrequired irregularities of reduce the influence of detection-unrequired irregularities as letterings, marks, codes, spews, an area to be detected by the electrostatic capacity sensor is set so as to have a long radial length and a short circumferential width. However, it could be seen that due to performance characteristics of an electrostatic capacity sensor, it is in fact difficult the conventional apparatus to separate signals caused by detection-unrequired irregularities from those caused by detection-required irregularities.
Consequently, it will be apparent that the inspection accuracy of the conventional apparatus is very low because of the fact that signals caused by such detection-unrequired irregularities as letterings, marks, codes, spews, and dirts on a tire side wall surface are frequently mistakenly discriminated as signals caused by detection-required irregularities.
Also, the conventional apparatus which utilizes a filter and the like is liable to generate detection signals having deformed waveforms and consequently further lowers the inspection accuracy.